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dc.contributor.advisorVan der Westhuizen, M. C.
dc.contributor.advisorDu Plessis, M. J.
dc.contributor.authorMabuda, Khathutshelo
dc.date.accessioned2018-04-03T08:12:39Z
dc.date.available2018-04-03T08:12:39Z
dc.date.issued2001-11
dc.identifier.urihttp://hdl.handle.net/11660/8075
dc.description.abstractEnglish: The objectives of this study were to investigate the effect of light, soil moisture and host plants on behaviour of Agrotis segetum (Denis & Schiffermuller). A marking technique for larvae was developed to study behaviour at night. The marker consisted of al: 1 mixture of Humbrol paint and fluorescent powder. It had no adverse effect on larval behaviour and survival. Dusting of larvae with fluorescent powder also proved useful in tracking movement for short range studies. Powder trails could be detected for a distance of up to two meters. The effect of illumination with different light sources i.e incandescent, infrared and UV light on activity of larvae was evaluated. Larvae were starved for 24, 48, 72 and 96 hours. Significantly more larvae that had been starved for 72 and 96 hours remained on the soil surface in search of food after an hour of illumination with infrared and UV light. Light and dark adaptation periods of 24,48 and 72 hours had an effect on larval activity. Phototaxis of A. segetum was therefore influenced by their degree of starvation and dark adaptation. Larvae moved towards the light source when illuminated with UV light under field conditions possibly perceiving it as a sign of open space. To evaluate the feeding behaviour of A. segetum larvae under wet and dry conditions, a greenhouse trial with Chenopodium carinatum R. Br., Portulaca oleracea L. and Zea mays L. was conducted. Significantly more above ground plant sections of all the three plant species were damaged under both dry and wet soil conditions. Larvae survived for approximately one week at soil moisture levels 10, 20, 40, 60, 80 and 100 % in the absence of food. To evaluate survival in the presence of food at various moisture levels, Amaranthus hybridus L. and P. oleracea were buried in separate pots at soil moisture levels 0, 10 and 80 %. All larvae remained alive for up to 10 days at the 80 % moisture level for each weed species. Larval survival was lowest at ° % soil moisture in both the absence and presence of food. Larval development was supported until pupation on A. hybridus at 80 % soil moisture. Agrotis segetum moths were given a choice between six plant species for oviposition. Eggs were laid on all plant species. Oviposition was however significantly higher on A. hybridus and 1. purpurea. Significantly more eggs were laid on stems than on the leaves. When laid on leaves, the abaxial was preferred over the adaxial surface. There was no significant difference in the number of eggs laid when given a choice between Vetiveria zizanioides (L.) Nash and Pennisetum purpureum (K.) Schumach. Dry leaves of P. purpureum and V. zizanioides were more preferred for oviposition than fresh plant sections. Plants selected by moths for oviposition are not always appropriate hosts for newly emerged larvae. Larval survival was low on some of the plants preferred for oviposition. First instar larvae were notable to feed on the grasses, P. purpureum, V. zizanioides and Z. mays and died while in the first instar. Survival and mass gain of first instar larvae fed on A. hybridus and C. album was significantly higher than on the rest of the plant species. Presence of these plant species in uncultivated maize fields seems to contribute to high population levels due to their suitability as hosts. Leaf trichome density on the plant species evaluated could however not account for the differences in survival and development of A. segetum larvae. The type rather than density of trichornes could be inhibitory or stimulatory to oviposition and larval survival of A. segetum.en_ZA
dc.description.abstractAfrikaans: Die doel van hierdie studie was om die effek van lig, grondvog en verskillende gasheerplante op die gedrag van die gewone snywurm, Agrotis segetum (Denis & Schiffermuller) te ondersoek. 'n Tegniek is ontwikkel om larwes te merk om hul gedrag gedurende die nag te bestudeer. Die merker bestaan uit 'n 1:1 mengsel van Humbrol verf en fluoresserende poeier en het geen nadelige effek op die larwes se gedrag en oorlewing gehad nie. Larwes wat in fluoresserende poeier gerol is, het 'n poeier-spoor agtergelaat tydens beweging, wat dit moontlik gemaak het om bewegings snags oor kort afstande te monitor. Poeiermerke kon vir afstande van tot twee meter gevolg word. Die effek van lig uit verskillende bronne op die aktiwiteit van larwes is geëvalueer. Larwes is uitgehonger vir 24, 48, 72 en 96 uur en belig met onderskeidelik 'n gloeilamp, infrarooi en ultraviolet lig. Na 'n uur van beligting met infrarooi en UV-lig het die aantal larwes wat uitgehonger is vir 72 en 96 uur betekenisvol meer op die grondoppervlak geblyopsoek na kos as dié wat vir 24 en 48 uur uitgehonger is. Fototaksis van die larwes is dus onderdruk deur hul graad van uithongering te verhoog. Die duur van periodes vir lig-aanpassing (24, 48 en 72 uur onderskeidelik), het ook invloed op die aktiwiteit van die larwes gehad. Onder veldtoestande het larwes in die rigting van die UV-ligbron beweeg en het dit moontlik as 'n oop ruimte waargeneem. Om die voedingsgedrag van A. segetum larwes onder nat en droë toestande te evalueer, is 'n glashuisproef gedoen met die gasheerplante Chenopodium carinatum R. Br., Portulaca oleracea L. asook Zea mays L. Betekenisvol meer bo- as ondergrondse dele van al drie plantspesies is beskadig onder beide nat en droë toestande. In die afwesigheid van kos, het larwes vir ongeveer 'n week oorleef by grondvogvlakke van 10, 20, 40, 60, 80 en 100 %. Om oorlewing in die teenwoordigheid van kos by verskillende vlakke van grondvog te evalueer, is Amaranthus hybridus L. en P. oleracea is in afsonderlike potte begrawe by grondvogvlakke 0, 10 en 80 %. Alle larwes het by 80 % grondvog tot 10 dae oorleef op beide A. hybridus en P. oleracea. Oorlewing van larwes was die laagste by 0 % grondvog in beide die teenwoordigheid en afwesigheid van kos. Larwale ontwikkeling tot papiewording het slegs plaasgevind op A. hybridus by 80 % grondvog. In 'n keuse-proef is Agrotis segetum motte toegelaat om te kies tussen ses plantspesies, naamlik Amaranthus hybridus L., Chenopodium album L., Datura stramonium L., Ipomoea purpurea (L.) Roth., P. oleracea and Z. mays vir eierlegging. Eiers is op al die plantspesies gelê, maar eierlegging was betekienisvol hoër op A. hybridus en l.purpurea. Meer eiers is op die stamme as die blare van plante gelê. Die abaksiale is bó die adaksiale blaaroppervlak gekies vir eierlegging. In 'n keuse-toets vir eierlegging tussen die grasse, Pennisetum purpureum (K.) Schumach, Vetiveria zizanioides (L.) en Z. mays, was daar was geen betekenisvolle verskil in die aantal eiers wat per plantspesie gelê is nie. Droë blare van P. purpureum en V. zizanioides is verkies bo vars plantdele. Plante wat deur motte vir eierlegging verkies word, is nie altyd geskikte gashere vir pas uitgebroeide larwes nie. Eerste-instar larwes was nie instaat om op die grasse, P. purpureum en V. zizanioides te voed nie en het as eerste-instar larwes doodgegaan. Oorlewing en massa toename van eerste instar larwes wat op A. hybridus en C. album gevoed het, was betekenisvol hoër as op die res van die plantspesies. Indien A. hybridus en C. album plante in onbewerkte mielielande voorkom, kan hulle dus bydra tot hoë populasievlakke van A. segetum as gevolg van hul geskiktheid as gasheerplante. Die digtheid van trigome op blare, kon nie 'n verklaring bied vir die verskille in oorlewing en ontwikkeling van A. segetum larwes op verskillende gasheerplante nie. Die tipe, eerder as die digtheid van die trigome kan onderdrukkend of stimulerend vir eierlegging en larwale oorlewing van A. segetum larwes wees.af
dc.description.sponsorshipARC-Professional Development Programmeen_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectDevelopmenten_ZA
dc.subjectGrassesen_ZA
dc.subjectLighten_ZA
dc.subjectMarkeren_ZA
dc.subjectMoistureen_ZA
dc.subjectOvipositionen_ZA
dc.subjectStarvationen_ZA
dc.subjectSurvivalen_ZA
dc.subjectTrichomesen_ZA
dc.subjectWeedsen_ZA
dc.subjectCutworms -- Ecologyen_ZA
dc.subjectPhytophagous insects -- Host plantsen_ZA
dc.subjectDissertation (M.Sc. (Zoology and Entomology))--University of the Free State, 2002en_ZA
dc.subjectInsect-plant relationshipsen_ZA
dc.titleEffect of soil moisture and host plants on behaviour and survival of the common cutworm, agrotis segetum (Denis & Schiffermüller) (Lepidoptera: Noctuidae)en_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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